Which of the following statements about molecular diagnosis is correct?

Options

A. PCR can detect high amounts of viral DNA present in the diseased patient.
B. ELISA incorporates the use of a radioactive probe which is allowed to hybridise to its complementary DNA.
C. PCR is powerful technique to identify different genetic disorders and is also used in the detection of mutated genes in suspected cancer patients,
D. Recombinant DNA technology is a risky method and hence is not used in molecular diagnosis.

Answer

To solve the question regarding which statement about molecular diagnosis is correct, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understand the context of molecular diagnosis**: Molecular diagnosis involves techniques that detect diseases at the molecular level, often through the identification of DNA, RNA, or proteins.

2. **Evaluate the first statement**: "PCR can detect the high amount of viral DNA present in the diseased patient."
- **Analysis**: This statement is incorrect. PCR (Polymerase Chain Reaction) is capable of detecting low amounts of viral DNA, not just high amounts. It is particularly useful for identifying infections even when the viral load is low.

3. **Evaluate the second statement**: "ELISA incorporates the use of radioactive probe which is allowed to hybridize to its complementary DNA."
- **Analysis**: This statement is also incorrect. ELISA (Enzyme-Linked Immunosorbent Assay) is based on antigen-antibody interactions and does not use radioactive probes. The technique that uses radioactive probes for hybridization is called Southern blotting.

4. **Evaluate the third statement**: "PCR is a powerful technique to identify different genetic disorders."
- **Analysis**: This statement is correct. PCR is widely used to identify various genetic disorders and can also detect mutated genes in cancer patients. This makes it a powerful tool in molecular diagnosis.

5. **Evaluate the fourth statement**: "Recombinant DNA technology is a risky method and hence it is not used in molecular diagnosis."
- **Analysis**: This statement is incorrect. Recombinant DNA technology is extensively used in molecular diagnosis and is not considered too risky for this purpose. It allows for the early detection of diseases.

6. **Conclusion**: After evaluating all the statements, the only correct statement is the third one: "PCR is a powerful technique to identify different genetic disorders."

### Final Answer:
The correct statement about molecular diagnosis is option 3: "PCR is a powerful technique to identify different genetic disorders."